Transmission apparatus and method, and reception apparatus and method

ABSTRACT

A transmission power control apparatus capable of reducing unnecessary transmission power that is consumed in transmission of pilot symbols. In the apparatus, a power control part establishes, based on a repetition number of a data signal, a transmission power value of a pilot signal. For example, the power control part establishes, based on an improved reception quality when data signals as replicated in accordance with the repetition number of a data signal are combined, a transmission power value of a pilot signal at a level required and sufficient for meeting a target value of the reception quality of the other end of communication. A power amplifying part amplifies the pilot signal in accordance with the established transmission power value.

This is a continuation application of application Ser. No. 11/722,859filed Jun. 26, 2007, which is a national stage of PCT/JP2005/023807filed Dec. 26, 2005, which is based on Japanese Application No.2004-380979 filed Dec. 28, 2004, the entire contents of each which areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a transmission power control apparatusand transmission power control method that perform transmission powercontrol of pilot symbols used in transmission channel estimation inradio communication systems. The present invention also relates to atransmission channel estimation apparatus and transmission channelestimation method that perform transmission channel estimation usingthese pilot symbols.

BACKGROUND ART

In recent years, in radio communications, especially in mobilecommunications, in addition to voice, various information includingimage is transmitted. Along with this diversification of media oftransmission, technologies for enabling high-speed transmission ofinformation are in demand. The OFDM (Orthogonal Frequency DivisionMultiplexing) scheme is a multicarrier transmission scheme havingfeatures of high spectrum efficiency and low inter-symbol interferencein the multipath environment, and is currently a focus of attention as atransmission scheme that may meet the above-noted demand.

In a radio communication system adopting the OFDM scheme, for example,at the transmitting side, a plurality of the same data symbols aregenerated by duplicating a data symbol (hereinafter this process will bereferred to as “repetition”) in the frequency domain (that is, on aplurality of subcarriers), and, at the receiving side, these symbols arecombined (using, for example, maximum ratio combining). In the followingdescription, OFDM schemes involving the above processing will bereferred to as “repetition OFDM”. In this ease, the received quality ofdata symbols (for example, SNR: Signal to Noise Ratio, and SIR: Signalto Interference Ratio) is improved by combining. A subcarrier may bereferred to as a “tone”.

Also, to implement high-speed transmission, it is important to maintainthe reception performance at the receiving side at a certain level orhigher, and, for this purpose, adequate control for accuratetransmission channel estimation is necessary. For example, patentdocument 1 proposes a method for controlling transmission power forpilot symbols used in transmission channel estimation and controllingthe accuracy transmission channel estimation. Specifically, patentdocument 1 proposes controlling transmission power for pilot symbolsaccording to the modulation scheme and coding rate of data symbols. Forexample, a modulation scheme that is less robust to frequency selectivefading requires high accuracy in transmission channel estimation, and,consequently, the transmission power of pilot symbols is increased. Onthe other hand, a modulation scheme that is more robust to frequencyselective fading does not require so much accuracy in transmissionchannel estimation, and, consequently, the transmission power of pilotsymbols is decreased.

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2003-60609

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, if the above conventional transmission power control method issimply applied to the above-mentioned repetition OFDM, the followingproblem arise. In repetition OFDM, as noted above, a plurality of thesame data symbols are combined and thereby the received quality of datasymbols improves. In other words, in this case, transmission power forpilot symbols required to ensure a certain level of receptionperformance or higher decreases. On the other hand, with conventionaltransmission power control methods, the transmission power of pilotsymbols is controlled, regardless of the improvement of received qualityof data symbols after combining. Transmission power of pilot symbols maythus be excess, and unnecessary transmission power is consumed intransmission of pilot symbols.

It is therefore an object of the present invention to provide atransmission power control apparatus, transmission channel estimationapparatus, transmission power control method and transmission channelestimation method that are able to reduce unnecessary transmission powerconsumed in transmission of pilot symbols.

Means for Solving the Problem

A transmission power control apparatus of the present invention adopts aconfiguration having: a setting section that sets a transmission powervalue for a pilot signal based on the number of repetitions of a datasignal; and an amplifying section that amplifies the pilot signalaccording to the transmission power value.

A transmission channel estimation apparatus of the present inventionadopts a configuration having: an attenuation section that attenuates apilot signal amplified according to a transmission power value, saidtransmission power value being set based on the number of repetitions ofa data signal; and an execution section that executes transmissionchannel estimation using the attenuated pilot signal.

A transmission power control method of the present invention has thesteps of: setting a transmission power value for a pilot signal based onthe number of repetitions of a data signal; and amplifying the pilotsignal according to the transmission power value.

A transmission channel estimation method of the present invention hasthe steps of: attenuating an amplified pilot signal according to atransmission power value set based on the number of repetitions of adata signal; and executing transmission channel estimation using theattenuated pilot signal.

Advantageous Effect of the Invention

According to the present invention, it is possible to reduce unnecessarytransmission power consumed in transmission of pilot symbols.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a base stationapparatus, according to Embodiment 1 of the present invention;

FIG. 2 is a flowchart showing the operations of a power control section,according to Embodiment 1 of the present invention;

FIG. 3 shows a reference table for power control use, according toEmbodiment 1 of the present invention;

FIG. 4 explains transmission power values for pilot symbols mapped on aradio frame, according to Embodiment 1 of the present invention;

FIG. 5 shows an example of pilot symbols arrangement, according toEmbodiment 1 of the present invention;

FIG. 6 explains an example of fluctuation of required SNR, according toEmbodiment 1 of the present invention;

FIG. 7 explains an example of the degree of reception performancedegradation in association with the transmission power ratio, accordingto Embodiment 1 of the present invention;

FIG. 8 shows transmission power that is reducible according to thenumber of repetitions, according to Embodiment 1 of the presentinvention;

FIG. 9 is a block diagram showing a configuration of a communicationterminal apparatus, according to Embodiment 2 of the present invention;and

FIG. 10 explains the operations of power correction section, accordingto Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail belowusing the accompany drawings.

Embodiment 1

FIG. 1 is a block diagram showing a configuration of a base stationapparatus provided with a radio transmitting apparatus according toEmbodiment 1 of the present invention. Base station apparatus 100 ofFIG. 1 has: antenna 101; radio receiving section 102; GI (GuardInterval) removing section 103; FFT (Fast Fourier Transform) section104; (Parallel-to-Serial) conversion section 105; demodulation section106; decoding section 107; modulation parameter determining section 108;power control section 109; power amplifying section 110; coding section111; modulation section 112; repetition section 113; multiplexingsection 114; IFFT (Inverse Fast Fourier Transform) section 115; GIaddition section 116; and radio transmitting section 117. Also, radioreceiving section 102, GI removing section 103, FFT section 104, P/Ssection 105, demodulation section 106 and decoding section 107constitute a receiving section. Modulation parameter determining section108, power control section 109, power amplifying section 110, codingsection 111, modulation section 112, repetition section 113,multiplexing section 114, IFFT section 115, GI addition section 116 andradio transmitting section 117 constitute a transmitting section of aradio transmitting apparatus.

Radio receiving section 102 receives a radio signal transmitted from acommunicating party, via antenna 101, and performs predetermined radioprocessing (for example, down-converting and A/D conversion) on theradio signal. The received signal after radio processing is outputted toGI removing section 103. GI removing section 103 removes the GI added ina predetermined position in the received signal. The received signalafter GI removal is outputted to FFT section 104. FFT section 104performs FFT processing on the received signal after GI removal. P/Ssection 105 performs parallel-to-serial conversion on the receivedsignal after FFT processing. Demodulation section 106 demodulates thereceived signal after parallel-to-serial conversion. Decoding section107 decodes the received signal after demodulation.

Modulation parameter determining section 108 obtains transmissionchannel information included in the received signal decoded by decodingsection 107, extracts information indicating the received SNR of thepilot symbols from the transmission channel information and reports thisinformation to power control section 109. The received SNR is a measuredvalue obtained by performing received quality measurement at thecommunicating party. In addition, the transmission channel informationis generated at the communicating party, multiplexed in a radio frame,and fed back from the communicating party. Further, the informationshowing the received SNR of the pilot symbols is generated at thecommunication party.

Also, modulation parameter determining 108 decides modulation parametersbased on the obtained transmission channel information. With thisembodiment, modulation parameters includes the coding rate used incoding at coding section 111, the modulation scheme used in modulationat modulation section 112 and the number of repetitions used inrepetition at repetition section 113. The decided coding rate,modulation scheme and number of repetitions are reported to codingsection 111, modulation section 112, and repetition section 113 andpower control section 109, respectively.

Coding section 111 encodes transmission data using the coding ratereported from modulation parameter determining section 108. Modulationsection 112 modulates the encoded transmission data using the modulationscheme reported from modulation parameter determining section 108. Bymeans of this modulation, data symbols are obtained. Modulation schemesfor use include, for example, BPSK (Binary Phase Shift Keying), QPSK(Quadrature Phase Shift Keying) and 16 QAM (Quadrature AmplitudeModulation).

Repetition section 113 performs repetition processing of the datasymbols according to the number of repetitions reported from modulationparameter determining section 108. One or more data symbols (forexample, R data symbols) obtained by repetition processing of one datasymbol, are outputted to multiplexing section 114.

Here, the number of repetitions means the number of data symbols afterrepetition of one data symbol. Specifically, when the number ofrepetitions is “1”, the number of data symbols after repetition is “1”.In this case, when a data symbol is received as input from modulationsection 112, repetition section 113 outputs the data symbol as is. Whenthe number of repetitions is two or more, a data symbol is outputted inrepetition. For example, when the number of repetitions is “2”, thenumber of data symbols after repetition is “2”. In this case, when adata symbol is received as input from modulation section 112, repetitionsection 113 outputs the data symbol twice in repetition. Further, whenthe number of repetitions is “16”, the number of data symbols afterrepetition is “16”. In this case, when a data symbol is received asinput from modulation section 112, repetition section 113 outputs thedata symbol sixteen times in repetition.

Power control section 109 as a setting means sets the transmission powervalue for the pilot symbols to a level adequate to satisfy a targetreception quality value of the communicating party in accordance withthe received SNR and the number of repetitions reported from modulationparameter determining section 108. With this embodiment, power controlsection 109 sets the transmission power value for the pilot symbols bycalculating an amplification value for use in amplification at poweramplifying section 110. The calculated amplification value is reportedto power amplifying section 110. The operations of power control section109 will be described in detail later. Although it has been describedthat the amplification value is calculated at power control section 109,a configuration may be adopted where the amplification value iscalculated at the communicating party and fed back to power controlsection 109.

Power amplifying section 110 amplifies pilot symbols generated at apilot symbol generation section (not shown) according to theamplification value reported from power control section 109. Theamplified pilot symbols have the transmission power value set at powercontrol section 109. The amplified pilot symbols are outputted tomultiplexing section 114.

In other words, the transmission power control apparatus according tothis embodiment is configured by combining power control section 109 andpower amplifying section 110.

Multiplexing section 114 multiplexes the R data symbols inputted fromrepetition section 113 and the pilot symbol amplified by poweramplifying section 110 in a radio frame. The radio frame aftermultiplexing is outputted to IFFT section 115.

IFFT section 115 performs IFFT processing on the radio frame inputtedfrom multiplexing section 114. GI addition section 116 adds a GI in apredetermined position in the radio frame after IFFT processing. Radiotransmitting section 117 performs predetermined radio processing (forexample, D/A conversion and up-converting) on the radio frame after GIaddition, and transmits the radio signal after radio processing viaantenna 101.

Next, the operations at power control section 109 will be describedusing FIG. 2.

First, in step S1010, the amplification value (initial value) G iscalculated using the received SNR reported from modulation parameterdetermining section 108. Specifically, the amplification value G iscalculated by subtracting the reported received SNR from the requiredSNR (i.e., the target value of the received SNR).

Also, in step S1020, the offset value α corresponding to the number ofrepetitions reported from modulation parameter determining section 108,is obtained. With this embodiment, power control section 109 stores areference table for power control use, in advance. FIG. 3 shows anexample of this reference table for power control use. When thisreference table for power control use is used and, for example, thenumber of repetitions “2” is inputted, the offset value “−1” isobtained. Also, for example, if the number of repetitions “16” isinputted, the offset value “−10” is obtained. Accordingly, the absolutevalue of the offset value, that is, the difference between theamplification value G and the final amplification value Gf (describedlater) is increased following the increase of the number of repetitionsand decreased following the decrease of the number of repetitions. Bythis means, the setting of the transmission power value for the pilotsymbols is implemented. To be more specific, the transmission powervalue for the pilot symbols is decreased as the number of repetitionsincreases and is increased as the number of repetitions decreases.

The method of obtaining the offset value α is not limited to the aboveexample, and a function may be used that derives the correspondingnumber of repetitions from the inputted number of repetitions.Alternatively, the above method of using a table and the above-mentionedmethod of using a function may be used together. When a function is usedthat derives the corresponding number of repetitions from the inputtednumber of repetitions, it is possible to define more flexiblerelationships.

Also, the reference table for power control use can be updated inaccordance with transmission quality required by the system. Forexample, when the required transmission quality changes from 1% to 0.5%,the reference table for power control use may be updated.

Upon update of the table, the updated information may be reported to thecommunicating party.

Also, the processing order of step S1010 and step S1020 is notparticularly limited. The processing of step S1010 may be executed firstor the processing of step S1020 may be executed first.

Then, in step S1030, the amplification value G is corrected by addingthe offset value α to the amplification value G. By this correctionprocessing, final amplification value Gf is calculated. The calculatedfinal amplification value Gf is outputted to power amplifying section110 as the value to be used in the amplification of the pilot symbols.

A method has been described as an example with this embodiment wheretwo-step processing of determining the amplification value G (initialvalue) using the received SNR and then determining the finalamplification value Gf—that is, a method of obtaining the finalamplification value Gf indirectly from the received SNR—is adopted.However, it is equally possible to use a table or a function where bythe final amplification value Gf is obtained directly from the receivedSNR.

Next, pilot symbols multiplexed in a radio frame will be described. Asshown in FIG. 4, pilot symbols are mapped in predetermined positions ina radio frame. In this figure, P represents the transmission power valueof pilot symbols when the amplification value G is not corrected orbefore the amplification value G is corrected. If the offset value α isadded to this transmission power value P, the transmission power valueof the setting for the pilot symbols is obtained. The format of theradio frame generated by multiplexing pilot symbols and data symbols, isnot limited to the format shown in FIG. 4.

According to this embodiment, when the transmission power value of pilotsymbols is set in accordance with the number of repetitions (that is,when the degree of received quality improvement for data symbols bymeans of combining on the receiving side increases following theincrease of the number of repetitions), the transmission power value ofpilot symbols is decreased, and, on the other hand, when the degree ofreceived quality improvement for data symbols on the receiving side bymeans of combining decreases following the decrease of the number ofrepetitions, the transmission power value of pilot symbols is increased,so that it is possible to prevent pilot symbols from using excessivetransmission power and reduce unnecessary transmission power consumptionin pilot symbol transmission.

Prevention of excessive transmission power for a pilot symbols will bedescribed in detail below.

With repetition OFDM, “repetition symbols” (referring to data symbolsobtained by duplicating a data symbol) in a radio frame are combined atthe receiving side, and, as a result, the SNR after combining improves.On the other hand, as shown in FIG. 5, pilot symbols are transmitted inspecific positions in a radio frame and are usually not subject torepetition. In other words, as for the data symbols, it is possible toimprove the low-SNR environment by applying repetition. In contrast tothis, as for the pilot symbols, it is difficult to improve the low-SNRenvironment. Assuming that transmission channel estimation is performedusing low-SNR pilot symbols at the receiving side, transmission channelestimation values are calculated with numerous errors.

Accordingly, to prevent reception performance degradation due totransmission channel estimation errors, transmission power for pilotsymbols is controlled. FIG. 6 shows the required SNR per symbolsatisfying PER=1% when the number of repetitions is “1”, and therequired SNR per symbol satisfying PER=1% when the number of repetitionsis “16”. These values are obtained by computer simulation.

It is shown that, when the number of repetitions is “16”, the requiredSNR per symbol is 13.8 dB lower than when the number of repetitions is“1”. This is because the SNR after combining is improved by 13.8 dBcompared to the SNR without combining (that is, the SNR in the casewhere the number of repetitions is “1”).

On the other hand, when the number of repetitions is “16”, the SNR perpilot symbol decreases by 13.8 dB compared to the case where the numberof repetitions is “1”. Accordingly, transmission power control of pilotsymbols is necessary to ensure a certain level of reception performanceor higher.

Here, FIG. 7 will be referred to. FIG. 7 shows the degree of degradationat PER=1%, in association with the ratio of the transmission power valuefor data symbols to the transmission power value for pilot symbols.These values are obtained by computer simulation, and the simulationresult for the number of repetitions “16” and the simulation result forthe number of repetitions “1” are shown. The degree of degradation isthe increment amount of the required SNR—more specifically, it is theincrement on top of the PER characteristic of when ideal transmissionchannel estimation is performed. The value “0.5 dB” shown as the degreeof degradation at PER=1% is a tentative target value of receptionperformance.

According to the simulation result for the number of repetitions “1”,the degree of degradation in response to the increase of thetransmission power ratio is moderate. In contrast, according to thesimulation result for the number of repetitions “16”, the degree ofdegradation in response to the increase of the transmission power ratioin steep. It is then shown that, when the number of repetitions is “16”,and the transmission power value is increased by 13.8 dB, the degree ofdegradation is well below 0.5 dB which is the target value of the degreeof degradation. In other words, it is shown that excessive quality ofpilot symbols occurs. Referring to the example shown in FIG. 7, when thenumber of repetitions is “16”, about the same level of receptionperformance is achieved by increasing the transmission power value forpilot symbols 4 dB, as when the number of repetitions is “1”.

Also, as shown in FIG. 8, the quality of pilot symbols required toensure a certain level of reception performance decreases as the numberof repetitions increases and increases as the number of repetitionsdecreases. The transmission power that can be reduced with respect topilot symbols increases as the number of repetitions increases anddecreases as the number of repetitions decreases. This is because thedegree of reducing the influence of transmission channel estimationerror by combining data symbols increases as the number of repetitionsincreases. Accordingly, according to this embodiment, by performingtransmission power control such that the transmission power value forpilot symbols decreases as the number of repetitions increases andincreases as the number of repetitions decreases, it is possible toreduce unnecessary transmission power consumption.

Although a case has been described with this embodiment where thetransmission power of pilot symbols is controlled in accordance with thenumber of repetitions of data symbols, a method of controlling thenumber of pilot symbols in accordance with the number of repetitions ofdata symbols may be adopted.

Although a case has been described with this embodiment where a radiotransmitting apparatus is provided in a base station apparatus, theradio transmitting apparatus may be provided in a communication terminalapparatus. That is to say, the present invention can be applied to notonly downlink communications but also uplink communications.

Embodiment 2

FIG. 9 is a block diagram showing a configuration of a communicationterminal apparatus provided with a radio receiving apparatus accordingto this Embodiment 2. Communication terminal apparatus 200 of FIG. 9has: antenna 201; radio receiving section 202; GI removing section 203;FFT section 204; demultiplexing section 205; modulation parameterdetermining section 206; power correction section 207; power attenuationsection 208; transmission channel estimation section 209; transmissionchannel compensation section 210; demodulation section 211; and decodingsection 212.

Radio receiving section 202 receives a radio signal transmitted frombase station apparatus 100, described in Embodiment 1, via antenna 201.The radio signal is then subjected to predetermined radio processing(including down-conversion and A/D conversion). The received signal(radio frame) after radio processing is outputted to GI removing section203. GI: removing section 203 removes the GI added in a predeterminedposition in the radio frame. The radio frame after GI removal isoutputted to FFT section 204. FFT section 204 performs FFT processing onthe radio frame after GI removal. The radio frame after FFT processingis outputted to demultiplexing section 205.

Separation section 205 as an extraction means extracts the data symbolsand pilot symbols from the radio frame inputted from FFT section 204,thereby separating the data symbols and the pilot symbols. The extracteddata symbols and the extracted pilot symbols are outputted totransmission channel compensation section 210 and power attenuationsection 208, respectively.

Modulation parameter determining section 206 receives as inputtransmission channel information, generated in a transmission channelinformation generation section (not shown) and including informationsuch as the received SNR measured or calculated in a SNR calculationsection (not shown). Modulation parameter determining section 206extracts information indicating the received. SNR from the inputtedtransmission channel information, and reports this information to powercorrection section 207.

Also, modulation parameter determining section 206 decides the number ofrepetitions based on the inputted transmission channel information. Inother words, modulation parameter determining section 206 determines thenumber of repetitions “R” of the data symbols extracted bydemultiplexing section 205 based on the inputted transmission channelinformation. The determined number of repetitions is reported to powercorrection section 207. The method of deciding the number of repetitionsat modulation parameter determining section 206 is the same as themethod of deciding the number of repetitions at modulation parameterdeciding section 108 described in Embodiment 1.

Power correction section 207 sets the corrected value of the receivedpower value of the pilot symbols extracted by demultiplexing section 205(that is, the reception power value after correction). With thisembodiment, power correction section 207 calculates the amplificationvalue calculated at power control section 109 described in Embodiment 1,thereby setting corrected value of the received power value. Thecalculated amplification value is reported to power attenuation section208. The amplification value calculation in power correction section 207is performed in the same manner as the amplification value calculationmethod in power control section 109 described in Embodiment 1, based onthe received. SNR, the required SNR, and the number of repetitions.

The amplification value calculated by power correction section 207 maybe fed back to power control section 109.

Here, the correction of the received power value of pilot symbols willbe described in detail. FIG. 10 illustrates the correction of receivedpower on an IQ plane. In this figure, A1 represents the received powervalue of a pilot symbol before correction, A2 represents theamplification value calculated at power correction section 207, and A3represents the received power value of the pilot symbol aftercorrection. That is, power correction section 207 subtracts theamplification value A2 from a pilot symbol having the received powervalue A1, thereby obtaining a pilot symbol having the received powervalue A3.

Power attenuation section 208 attenuates the pilot symbols inputted fromdemultiplexing section 205 according to the amplification value reportedfrom power correction section 207. In other words, power attenuationsection 208 attenuates the power amplified at power amplifying section110 of base station apparatus 100 from the pilot symbols. The attenuatedpilot symbols are outputted to transmission channel estimation section209.

Transmission channel estimation section 209 executes transmissionchannel estimation using the pilot symbols inputted from powerattenuation section 208, and obtains a transmission channel estimationvalue. The obtained transmission channel estimation value is outputtedto transmission channel compensation section 210.

In other words, a transmission channel estimation apparatus of thisembodiment is configured by combining modulation parameter determiningsection 206, power correction section 207, power attenuation section 208and transmission channel estimation section 209. The transmissionchannel estimation apparatus performs transmission channel estimationusing the extracted pilot symbols based on the number of repetitions ofthe data symbol, and obtains a transmission channel estimation value.Also, with the transmission channel estimation apparatus, the receivedpower value of the pilot symbols is correction as described above, andthe transmission channel estimation value is compensated in theamplitude direction. Specifically, in the amplitude direction, thetransmission channel estimation value is increased following theincrease of the number of repetitions and is decreased following thedecrease of the number of repetitions.

Transmission channel compensation section 210 performs transmissionchannel compensation on the data symbols inputted from demultiplexingsection 205 based on the transmission channel estimation value inputtedfrom transmission channel estimation section 209. The data symbolssubjected to transmission channel compensation are outputted todemodulation section 211.

Demodulation section 211 combines the R data symbols inputted fromtransmission channel compensation section 210 and then demodulates thedata symbols. In demodulation, the same modulation scheme is used as inmodulation section 112 described in Embodiment 1. Decoding section 212decodes the demodulated data symbols, thereby obtaining the receiveddata.

In this way, according to this embodiment, when transmission channelestimation is performed according to the number of repetitions (that is,when the degree of received quality improvement for data symbols bymeans of combining increases following the increase of the number ofrepetitions), the transmission power value for pilot symbols isdecreased on the transmitting side and the transmission channelestimation value is increased in the amplitude direction, and, on theother hand, when the degree of received quality improvement for datasymbols by means of combining decreases following the decrease of thenumber of repetitions, the transmission power value for pilot symbols isincreased on the transmitting side and the transmission channelestimation value is decreased in the amplitude direction, so thatchanges in the amplitude direction caused by transmission power controlare corrected on the receiving side and the accuracy of transmissionchannel estimation values in the amplitude direction is maintained,consequently improving reception performance for data symbols subjectedto M-ary modulation.

Although a case has been described with this embodiment wheretransmission channel estimation is performed after the received powervalue of pilot symbols is corrected according to the number ofrepetitions, compensation may be performed after transmission channelestimation. Further, correction may be performed after R data symbolsare combined.

Although a case has been described with this embodiment, where a radiotransmitting apparatus is provided in a base station apparatus, thisradio transmitting apparatus may be provided in a communication terminalapparatus. In other words, the present invention can be applied to notonly downlink communications but also uplink communications.

This concludes the description of embodiments of the present invention.However, the present invention can be implemented by modifying the aboveembodiments. For example, although with the above embodiments eases havebeen described where the present invention is configured by hardware,the present invention may be implemented by software.

The base station apparatuses in the above embodiments may be referred toas “Node B”, and a communication terminal apparatus may be referred toas “UE”.

Also, although with the above embodiments, the SNR is used as an ofindicating measured reception quality, available indicators are notlimited to this. It is possible to use, for example, the SIR, SINR(Signal to Interference and Noise Ratio), CIR (Carrier to InterferenceRatio), CNR (Carrier to Noise Ratio), CINR (Carrier to Interference andNoise Ratio), RSSI (Received Signal Strength Indicator), receivedintensity, received power, interference power, error rate, transmissionrate, throughput, amount of interference, and MCS (Modulation and CodingScheme) that can achieve a predetermined error rate. Also, informationindicating reception quality may be represented as, for example, CQI(Channel Quality Indicator) or CSI (Channel State Information).

In addition, each of functional blocks employed in the description ofthe above-described embodiment may typically be implemented as an LSIconstituted by an integrated circuit. These are may be individual chipsor partially or totally contained on a single chip.

“LSI” is adopted here but this may also be referred to as an “IC”,“system LSI”, “super LSI”, or “ultra LSI” depending on differing extentsof integration.

Further, the method of integrating circuits is not limited to the LSI's,and implementation using dedicated circuitry or general purposeprocessor is also possible. After LSI manufacture, utilization of FPGA(Field Programmable Gate Array) or a reconfigurable processor whereconnections or settings of circuit cells within an LSI can bereconfigured is also possible.

Furthermore, if integrated circuit technology comes out to replace LSI'sas a result of the advancement of semiconductor technology or derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application in biotechnology isalso possible.

The present application is based on Japanese Patent Application No.2004-380979, filed on Dec. 28, 2004, the entire content of which isexpressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

The transmission power control apparatus, transmission channelestimation apparatus, transmission power control method and transmissionchannel estimation method of the present invention can be applied tobase station and communication terminal apparatus in a radiocommunication system where pilot symbols used for transmission channelestimation are transmitted with data symbols.

1. A transmission apparatus comprising: a setting section that sets atransmission power for a pilot signal based on the number of repetitionsof a data signal; an amplifying section that amplifies the pilot signalaccording to the transmission power; and a transmitting section thattransmits the amplified pilot signal and the data signal which aretime-multiplexed.
 2. The transmission apparatus according to claim 1,wherein the setting section sets the transmission power based onreception quality for data signals that are duplicated according to thenumber of repetitions and that are combined.
 3. The transmissionapparatus according to claim 1, wherein the setting section sets thetransmission power based on a target value for reception quality in acommunicating party.
 4. The transmission apparatus according to claim 1,wherein the setting section sets the transmission power at a leveladequately satisfying a target value for reception quality in acommunicating party.
 5. The transmission apparatus according to claim 1,further comprising a repetition section that duplicates a data signalaccording to the number of repetitions, wherein said transmittingsection transmits the amplified pilot signal and the duplicated datasignals which are time-multiplexed.
 6. A reception apparatus comprising:a receiving section that receives a pilot signal and a data signal whichare time-multiplexed and transmitted from a transmission apparatus; andan estimating section that performs a channel estimation based on thepilot signal, wherein the pilot signal transmitted from the transmissionapparatus is amplified according to a transmission power which is setbased on the number of repetitions of the data signal.
 7. The receptionapparatus according to claim 6, further comprising an attenuationsection that attenuates the received pilot signal, wherein saidestimating section performs the channel estimation based on theattenuated pilot signal.
 8. A transmission method comprising: setting atransmission power for a pilot signal based on the number of repetitionsof a data signal; amplifying the pilot signal according to thetransmission power; and transmitting the amplified pilot signal and thedata signal which are time-multiplexed.
 9. A reception methodcomprising: receiving a pilot signal and a data signal which aretime-multiplexed and transmitted from a transmission apparatus; andperforming a channel estimation based on the pilot signal, wherein thepilot signal transmitted from the transmission apparatus is amplifiedaccording to a transmission power which is set based on the number ofrepetitions of the data signal.